1. Field of the Invention
The present invention relates to a gear structure of a transmission configured to achieve gear-shift between a plurality of gear positions when a single shift sleeve is operated.
2. Description of the Related Art
A conventional transmission is configured to achieve gear-shift between a plurality of gear positions when a single shift sleeve is operated. FIG. 6 shows such a conventional transmission. At the right end of an input shaft 100 for changing gear, a low gear 110 for low-speed forward movement, and a high gear 120 for high-speed forward movement are arranged adjacent to each other in the axial direction. Then, a reverse gear 130 for backward movement is arranged at the left end of the input shaft 100. Further, at the center, a shift sleeve 140 is axially movably spline-fit.
The low gear 110 includes a boss part 111 extending leftward from a low-gear body part 113 provided with gear teeth formed on the outer periphery thereof and is rotatably fit onto the input shaft 100 with a needle bearing in between. Then, dog claws 112 are formed at the left end of the boss part 111.
The high gear 120 includes a cylindrical part 121 extending so as to open leftward from a high-gear body part 123 provided with gear teeth formed on the outer periphery thereof, and is rotatably fit onto the outer periphery of the boss part 111 with a needle bearing in between. Then, dog claws 122 are formed at the left end of the cylindrical part 121.
The reverse gear 130 includes dog claws 131 formed on the right end surface of the reverse gear body part provided with gear teeth formed on the outer periphery thereof, and is rotatably fit onto the input shaft 100 with a needle bearing in between.
The shift sleeve 140 includes dog claws 141 for backward movement formed in the left end and dog claws 142 for forward movement formed in the right end. When the shift sleeve 140 is moved in an axial direction so that the shift sleeve 140 is brought into dog coupling to any one of the reverse gear 130, the low gear 110, and the high gear 120, transmission of a driving force is achieved between the input shaft 100 and any one of the gear 110, 120, or 130 fit rotatably onto the input shaft 100.
At the left side of the boss part 111 of the low gear 110, a press body 102 is provided that is fit and inserted between the dog claws 112 in the axial direction and extends outwardly in the diameter direction. The press body 102 abuts approximately against the left end of the boss part 111 and abuts approximately against the left end of the high-gear body part 123 of the high gear 120. This achieves positioning of the left ends of both gears 110 and 120 in the axial direction. The press body 102 is axially non-movably arranged on the input shaft 100 with washers 103 and 104 by using a circlip 105. As a prior art reference, Japanese Laid-Open Patent Publication No. 2002-213611 is known.
Meanwhile, when the low gear 110 and the high gear 120 are to be attached to the input shaft 100, first, the low gear 110 is attached to the outer periphery of the input shaft 100 with the needle bearing in between. Then, in a manner of being adjacent to the left side of the low-gear body part 113 with a washer 106 in between, the high gear 120 is attached to the outer periphery of the boss part 111 from the left side with a needle bearing in between. After that, in a manner of being fit and inserted between the dog claws 112 in the axial direction, the press body 102 is attached so as to abut approximately against the left end of the boss part 111 and the left end of the high-gear body part 123. Further, at the left end surface of the press body 102, the circlip 105 is axially non-movably arranged on the input shaft 100 with the washers 103 and 104.
In this case, after the high gear 120 is attached, the press body 102, the washers 103 and 104, and the circlip 105 need be attached to the inner side of the cylindrical part 121 from the left side. Thus, assembly workability of these components and checking workability of the assembled state have required time and effort.